According to M. Litt and T. Matsuda, J. Appl. Polym. Sci. 19 (1975) 1221, zwitterionic sulfonate-containing siloxanes are obtained by reaction of aminoalkyl functional silanes/siloxanes with .omega.-alkyl sultones. Although .omega.-alkyl sultones are reactive, as a rule they are also toxic and carcinogenic. Such compounds can be used only in special plants with high safety regulations. Use of the zwitterionic siloxanes obtained by this process is highly undesirable because of the residual content of .omega.-alkylsultones.
In U.S. Pat. No. 5,532,399 (Wacker-Chemie GmbH, issued on Jul. 2, 1996), ionic siloxanes are prepared by first producing via a nucleophilic substitution by sulfite ions on chloropropylsilanes and simultaneous hydrolysis, a sulfonate-functional siloxane hydrolysate, from which a sulfonic acid-functional siloxane hydrolysate is formed by acidification, which finally can be equilibrated with amine-functional silanes/siloxanes and further siloxanes to give a zwitterionic siloxane which carries ammonium and sulfonate groups.